1. Field of Invention
This invention relates to dipole antennas used for receiving and transmitting radio frequency energy.
2. Prior Art
There is a long history of man's attempt to create antennas that are small and compact in size with performance equal to those antennas of significantly larger dimension. The driving forces behind this movement are the wish for convenience and low cost. A good example of such small and compact spiral antenna is that one called the “spider web.” This antenna was used in the early days of radio for the reception of AM broadcast in the home; it was made from wires placed onto a wood frame in a spiral fashion. This antenna most often was placed on top of or alongside the AM radio which was housed inside a beautifully finished wood cabinet.
The science of antennas continues to move forward thanks to the use of sophisticated test instrumentation not available to our predecessors. The development in material science has made concomitant advancement. Man continues to learn and makes improvements in old designs—this is called Progress.
I submit this Patent Application on the improvement of the resonant and balanced dipole antenna prior art as submitted by Brown—U.S. Pat. No. 3,432,858 dated Mar. 11, 1969 regarding his Short Dipole Antenna. Reference will be made to others who experimented with similar devices but did not achieve the goal and performance that I have.
Dipole antennas are primarily designed to have balanced radio frequency (RF) antenna current at resonance at a primary frequency. The antenna described in this patent has unbalanced RF antenna current and has a plurality of resonant frequencies. This antenna has merits of utility, notable performance advantages and useful benefits not previously exploited with dipole antennas. Additionally, this resonant and unbalanced antenna has efficient and effective performance even though this it is uniquely smaller in physical size than those customarily used on the same operating frequency.
The primary objective of Mr. Brown was to create a short dipole antenna that had radiating elements placed perpendicular to the ground; such antenna is called a vertical dipole due to its physical orientation. He asserts—per specification lines 2-47 to 52—that the optimum height above ground for his invention is ⅜ (0.375) wavelength in order to achieve maximum distance for reception or transmission. There is no optimum height needed for my invention; my antenna operates with good performance as low as 0.037 wavelength distance from the ground with both vertical and horizontal orientation.
Mr. Brown's invention—as per lines 2-60 and 61 is “tuned to receive signals efficiently at two relatively widely spaced operating frequencies.” My invention both receives and transmits efficiently at many frequencies—closely or widely spaced—and at any number of frequencies combinations as selected by the user.
Mr. Brown's invention requires—per line 4-45—“in actual practice” the use of a loading device “56 or 58” to resonant his antenna so that “it appears as a resistive load for the transmission line”—lines 4-50 and 51. My antenna needs no such supplementary devices or components for loading, impedance matching or to achieve resonance in order to appear as a resistive load for the transmission line.
Of vital importance to the reader is that Mr. Brown asserts that his end spirals elements are for tuning purposes and that the radiating portion of his antenna are the co-linear short metal segments placed between the transmission line and the end spiral wire elements—lines 2-11 to 19, 37 to 39. Indeed, he asserts that he wishes to “minimize radiation therefrom (sic. spirals) and to concentrate radiation of the antenna structure in the radiating elements (sic. co-linear short metal segments) themselves.”—lines 2-43 to 45. According to his design, his spiral and radiating portion of the antenna “provide a balanced antenna”—lines 2-16 & 17. My antenna invention—operating on the reverse philosophy—uses the end spiral wire elements for maximum RF antenna radiation in an unbalanced state with any radiation from its co-linear short metal segments, that is the connecting wires, being minimal. The reader will thus notice two completely different phenomena when comparing Mr. Brown's antenna with my antenna invention.
Mr. Brown's antenna needs a special device in order to be fed with coax transmission line.—lines—specification lines 3-8 to 10 and FIG. 4. My antenna invention can be directly connected to coax transmission line without the need for any kind additional devices of any sort.
With regard to the points of electrical connection to each spiral, he asserts that “these points of connection are preferably in the same general areas of each spirally-wound coil to provide a completely balanced structure”—specification lines 4-68 to 71. The design of my invention is such that the points of electrical connection to each spiral are intentionally positioned at different locations which are widely spaced relative to each other and contribute to an unbalanced RF antenna current.
Mr. Brown's method of construction and choice of material is open to improvement. He makes no statement about the suitability of his antenna to outdoor weather exposure. My antenna is designed for long term outdoor exposure and extreme weather conditions.
Of critical importance is his “spiral support member” FIG. 1-28. Each support member retains the wire in place such that spiral geometry is achieved and, hopefully maintained in such geometry during extreme weather conditions. Yet he fails to specify the material composition of this most important item. Should it be made of metal, the notch FIG. 3-32 must have a width equal to the wire diameter in order to sit into rib FIG. 3-30. He fails to provide means to secure and retain the wire within the notch and thus it is most susceptible to coming out especially during high wind condition. Also, any water entrained in the notch will force the wire out of the notch when the water turns into ice as water expands upon freezing. Should Mr. Brown intend his notch 32 be made from plastic, he fails to specify the type of polymer.
The polymer formulation is extremely important as it must be resistant to Ultraviolet degradation and not fail due to repeated stress from expansion and contraction during hot and cold temperature cycling. A polymer, that is plastic, is most susceptible to degradation when exposed to outdoor elements.
Mr. Brown's invention employs a “pinch-clip” connector FIG. 1-30. He does not specify the material for this important item. It must be a metal alloy for electrical conduction as his spiral conductor is metal wire. He should have specified the metal alloy for his clip as any combination of dissimilar metals will undergo galvanic reaction and deteriorate in a short period time and cause electrical catastrophic failure of this critical connection. Using the same metal for his clip as the spiral wire will still deteriorate electrical conductance due to oxidation. Also, a pinch-clip connector is susceptible to dislocation from loosening of clamping pressure due to weathering and temperature cycling from metal expansion and contraction. The points of electrical connection to the spiral elements in my invention are soldered for permanence.
Mr. Brown wishes his antenna “to provide a balanced antenna structure”—lines 2-16 & 17. It is of utmost importance for the reader to discern that Mr. Brown does not claim the benefits of an antenna using an unbalance structure. Indeed, prior art appears oblivious to the many useful benefits obtained when the antenna RF current is in an unbalanced state!
Mr. Brown's invention is able to receive “two widely spaced frequency bands”—lines 5-52 & 53. He specifically cites both the 10 meter and 40 meter amateur bands. The centers of these two bands are 28.85 MHz and 7.15 MHz respectively; thus his wide spacing is 28.85/7.15=4.03 multiplying factor. He does not purport nor state that two widely spaced frequency bands can be transmitted on. Nor does he present his invention capable of receiving or transmitting on two closely spaced frequencies. My antenna improvements permit both receiving and transmitting on two or more frequencies whether they are widely or closely spaced.
On February 1970, Mr. Brown wrote an article for 73 Magazine which was devoted to ham radio enthusiasts. His article “An Eighteen Inch Dipole on Fifteen Meters” describes his antenna invention of U.S. Pat. No. 3,432,858 which he references on page 25 of that article. Of large importance, are his statements on page 25 which are marked “A” and “B” on the copy submitted with my application. Statement “A” shows that Mr. Brown's means for tuning “consists of telescoping brass tubings . . . ” and his statement “B” reads: “The antenna system comprises an end-loaded dipole with matching impedance in the center.” It is clear: Mr. Brown's invention frequency tuning is done primarily with the linear straight section of his antenna as he states—and again—he confirms that his antenna invention requires an impedance matching device—in the center—exactly as was shown in his patent drawing.
In said article, Mr. Brown calls his spiral antenna sections ‘coils.’ He refers to his spiral coils as “end-loading” devices. Such commonly used antenna end-loading devices are passive in nature and due to their passivity they are not designed, nor intended to be significant contributors of RF antenna radiation.
On page 28, the sentence marked “C” in the submitted 73 Magazine copy points out that Mr. Brown's antenna invention requires “a trap in each coil to permit operation on the two bands.”
An antenna “trap” is another commonly used antenna add-on device which is employed to obtain operation on a frequency other than the primary frequency for which the antenna is designed. Such “trap” is any suitable combination of capacitor, inductor or both. The purpose of the “trap” is to alter the antenna element circuit parameters of resistance and reactance so that a resonant condition appears. Thus, it is abundantly clear to the reader that Mr. Brown's antenna design—which he cites in said 73 Magazine article as “U.S. Pat. No. 4,432,858”—requires an extraneous antenna trap electrical components—added to his end spirals—in order for his antenna to work on a frequency other than the primary resonating frequency! No such devices whatsoever are found in my antenna invention.
In the March 1998 issue of WorldRadio, Mr. Petlowany published an article entitled “From out of the Past—antennas with a new twist.” It is a spiral dipole antenna. As he states in this article (marked “A” on the submitted copy), Mr. Petlowany's experiments led him to formulate what he calls “The Petlowany Principle” which states that “if a length of wire is wound into a spiral-shaped coil and excited by a radio frequency current connected to the innermost portion of the coil, it will then, and only then, exhibit RF characteristics that closely approximate those of a resonant linear wire of the same length.” It is clear that he does not purport his antenna to be resonant . . . only “closely approximate” and, as we read, he excludes any portion of the coil other than “the innermost portion.” Unknown to him, useful benefits are achieved when the radio frequency current connection is located on the spiral coil other than the innermost portion of the coil. His principle is made invalid with my antenna invention as the radio frequency current can be connected to any portion of the spiral coil and generates RF resonance exactly equivalent to those of a resonant linear wire.
Also, Mr. Petlowany's antenna has balanced RF antenna current. Again, Mr. Petlowany's antenna and my antenna invention are two completely different phenomena in operation.
There is a matter of vital importance to the reader in association with the experiments done by Mr. Petlowany: he employed a feed point current balun. Although he does not specifically mention this fact in the text of his article, he presents a photograph showing this device which is clearly labeled “Feedpoint current balun” (marked as “B” on the submitted copy.) As we know, a balun is used for impedance matching the antenna feed point with the characteristic impedance of the transmission line. Very simply stated, a balun is not required whatsoever with my antenna invention to achieve impedance matching.
Mr. Petlowany states in his article (marked as “C” on the submitted copy) that “If the linear portions are long enough in terms of the wavelength of the applied RF current, an appreciable amount of radiation takes place resulting in an efficient antenna.” The reader will notice that Mr. Petlowany's ‘linear portions’ in his antenna are the same function as the ‘co-linear segments’ of Mr. Brown's antenna and both gentlemen rely upon for this “linear” part of their respective antennas for primary antenna radiation. The spiral elements ARE the primary antenna radiators in my antenna invention and any “linear” portions have negligible radiation: completely reverse operation.
Mr. Petlowany states (marked as “D” in the submitted copy) that “Multibanding antennas are possible by using multiple coils to resonate the short linear portion of the antenna at the desired frequencies provided that sufficient spacing between coils is allowed to prevent detuning of the individual coils.” He does not state that “multibanding” is indeed inherently manifest without using multiple coils. Just as importantly, Mr. Petlowany relies upon the spiral coils to resonate the short linear portion in his antenna just as Mr. Brown relies upon the spiral tuning coils to resonate the short linear portion in that antenna.
In my antenna invention the spiral coils are the resonant portions of my antenna and the radiating portion of my antenna. My antenna provides true multiband performance without additional coils.
For the record, there was another article that was published in RadioWorld entitled “Variations on a Petlowany” by William Caldwell Sr. He describes his simple experiments with “Petlowany” antennas. His limited experience was strictly with a spiral antenna using one spiral element; he makes no mention of any linear portions or reference to radiating segments.
These magazine articles are written by Individual Amateur Radio enthusiasts. The experiments they performed are typical of what is referred to in that hobby as ‘homebrew’ construction. Such rough construction is of ‘one of a kind’, made with materials ‘on hand’, and by nature of such construction, not intended for long time use or commercialization.
The last category of prior art are cited patents that have some possible relationship to the present invention in this application. They are relevant as these cited patents utilized spiral antenna geometry. Inspection of these cited patents show significant departure from the invention of this application for the following reasons;                1.) Certain antennas have multiple spiral arms and/or exact Archimedes spiral formula;        2.) Certain antennas include inherent balun or other matching components;        3.) Certain antennas have spiral geometry that mechanically rotate to achieve tuning;        4.) Certain antennas use fractal geometry.        
The antenna invention presented in this application does not employ a motor for tuning; does not use exact Archimedes spiral geometry; does not employ a balun or other matching device; does not have spirals that rotate by mechanical means; does not use fractal geometry.